Since a so-called fluorine grease containing a fluorine synthetic oil as a base oil exhibits a poor oil solubility, various additives generally usable in a hydrocarbon lubricating agent is restrictively used to the fluorine grease. For instance, in order to impart wear resistance and an anticorrosion function to the fluorine grease, sodium nitrite (i.e., an inorganic passivation agent) has been used for a long time. However, sodium nitrite is known for reacting with a secondary amine under acid conditions to generate N-nitrosamine. Since N-nitrosamine is an environmentally burdening substance, an additive capable of functioning in place of sodium nitrite has been desired.
In such circumstances, a fluorine grease containing at least one of an aliphatic dicarboxylic acid metal salt, a monoamide monocarboxylic acid metal salt or a monoester carboxylic acid metal salt as a thickener has been proposed (see, for instance, Patent Literature 1). Patent Literature 1 discloses that this fluorine grease exhibits excellent wear resistance, leakage resistance and detergency and producible at a satisfactory cost. Moreover, a fluorine grease containing polytetrafluoroethylene as the thickener and a fatty acid metal salt (e.g., sebacic acid metal salt) as a rust inhibitor has been proposed (see, for instance, Patent Literature 2). Patent Literature 2 discloses that the fluorine grease exhibits excellent evaporation characteristic and rust resistance.